1. Field of the Invention
The present invention relates to power presses and more particularly to a safety device for power presses.
2. Description of the Prior Art
The prior art includes U.S. Pat. Nos. 2,311,441; 2,115,322; 2,683,515; 2,798,583; 2,826,286; 4,070,940 and 4,220,032. Reference in particular is made to U.S. Pat. No. 4,220,032 which discloses a power press of the type provided for bending, forming, punching, slitting, slicing, or cutting a workpiece, such as a piece of sheet metal. A bending machine or press break conventionally includes a fixed lower die and a movable upper die which travels with the ram for bending a workpiece positioned by a human operator in a break between the dies. Such machines are actuated by the operator, often by a foot pedal, in order to free the hands of the operator for guiding and positioning the workpiece according to guide marks at the break in the machine. Conventionally, such machines include a workpiece-receiving surface, such as a table, which is used to guide the sheet metal into the machine to a particular position. Upon actuation of the machine, the movable die is reciprocated to perform the bending function on the positioned sheet metal.
It has been a continuing problem in the art to develop a safety mechanism to prevent a human operator from inserting his hands or fingers into such machinery during the work cycle. Such machines have in the past caused serious personal injury such as loss of fingers.
With respect to the aforesaid U.S. Pat. No. 4,220,032, a transparent guard is provided which raises and lowers in substantial synchronism with the reciprocating ram. A control mechanism serves to lower the transparent guard to a position in front of the break just prior to the movable die arriving thereat such that an operator cannot insert his fingers or hands into the break since the guard constitutes an interferring barrier. However, a problem with this arrangement is that should the operator have his fingers or hand underneath the guard prior to the lowering thereof, the ram nevertheless can continue its downward descent. The impact of the guard against the fingers or hand of the operator is the only safety precaution involved, and depends upon the sense of feel, since upon feeling the guard's impingement, the operator would normally withdraw his hands thereby perhaps avoiding the dies as they come together.